hi, I'm running out of ideas what could be wrong.
Many custom maps show skyboxes. I've read on forums and asked chatgpt. I have Quake v.1.32, without the osp/excessiveplus mods (I deleted the addons folders and the q3config file from the baseq3 folder so a new one could be created). I tried replacing the quake3.exe file from the base game.
Chat told me to create quake3.bat and autoexec.cfg files, various file variants to fix this bug.
He also told me to fix it from the console. I checked the /seta r_GL_LINEAR_MIPMAP_LINEAR command in the console on every version of Quake. The console doesn't read it at all; it defines it as a regular text message, the same goes for the commands:
/seta r_detailtextures 1
/seta r_finish 1

It only reads two commands:

seta r_roundImagesDown "0"
seta r_picmip "0"

I checked what it uses game on my laptop:
GL_VENDOR: NVIDIA Corporation
GL_RENERER: NVIDIA GeForce GTX 960M/PCie/SSE2
GL_VERSION: 4.6.0 NVIDIA 531.29

So I tried several versions, the standard 1.32, the one with the replaced quake3.exe file.

In ioquake, skyboxes render correctly, but there's a strange, constant screen brightening and dimming, and the textures flicker.
Chat generated text for me to create an autoexec.cfg file. I tried several times, asking for it for each option for each version of the game, but it still doesn't work.
Can anyone help?

@dzidek : Can you share the following please:

1. What exactly is you issue with the skyboxes in a concise statement.
2. With ioquake3, the screen dimming and brightening sounds you have r_hdr 1 enabled. In the console, try setting that to r_hdr 0. If that problem is still present, let me know.
3. Can you share the names of two or three maps that have the issue so we might be to see the issue ourself.

It also sounds ChatGPT has just spat out random options and commands for you :)

I may have written this a bit chaotically, but gpt helped me previously with creating supplementary files for map files where tm wasnt available, and what he wrote seemed logical. Unfortunately, I have no idea about all this, and the people on fb werent particularly helpful or provided solutions without explaining how to do it.
I included snippets of the chat conversations because there are too many.

The problem with skyboxes in v.1.32 was that you could see the black outlines of the map cube, which was very annoying during gameplay and spoiled the feeling of space.
But lets focus with ioquake, because with v.1.32 and skyboxes, I gave up. Ioquake doesnt have the skybox problem, and after entering the r_hr 0 command, the problem with pulsating lighting on maps disappeared.
But Ive played it now and noticed that the problem with flickering textures isnt limited to a custom map, sometimes textures flicker in the menu, for example, in the game settings menu, the bar for a given slot starts flickering slightly, so maybe the problem is somewhere in my laptop (10yo, Windows 10).
Its not currently bothersome, its just sporadic, but I hope it doesnt get worse over time. Returning to the maps and textures, here are the ones:

lvlworld.com/review/id:463
lvlworld.com/review/id:1969
lvlworld.com/review/id:1410
lvlworld.com/review/id:1555

The biggest problem is with coralctf.

ps. Im just wondering about the topic of the post, because ultimately its about textures, not skyboxes

AI slop won't help you fix those clamp seams because it's hardcoded behavior, spurred by ignorance on trusting nVidia's technical errors as 'the standard' too much way back then. All source ports fixed this since.
Edited 1.02 minutes after the original posting.

@dzidek : As leilei has stated, this is a hard-coded issue within the default Q3A game engine and is 100% related to a known bug released in nvida's (now) very old drivers.

This is a "you can't fix it" bug with that default engine. You need to use an updated engine like ioquake3 or Quake3e

That older laptop graphics card should be more than good enough to play Quake 3 on a new engine but could also be part of the issue with the screen flashing / menu issues. Tweaking your settings could help to resolve. I would be looking at options that disable new settings (like r_hdr 0) and trying to cut back as much as possible.